ora-00600: internal error code, arguments: [%s], [%s], [%s], [%s], [%s], [%s], [%s], [%s]
*Cause: This is the generic internal error number for Oracle program
exceptions. This indicates that a process has encountered an
exceptional condition.
*Action: Report as a bug - the first argument is the internal error number

=> Search on Metalink or/and call Oracle support.

Btw, 8.1.5 has been desupported since January 2001 so don't hope any help from Oracle. The only answer will be "upgrade".